祁连山北坡沙尘天气气溶胶特征的飞机观测

Aerosol Characteristics of Dust Weather on North Slope of the Qilian Mountains

了解沙尘天气下气溶胶的垂直分布特征对于进一步认识气溶胶-云相互作用及其天气、气候效应至关重要。基于2023年9月6日沙尘天气下的飞机观测数据,分析祁连山北坡沙尘气溶胶的垂直分布特征。结果表明:此次沙尘天气是在高空锋区及地面冷高压的共同作用下形成。受沙尘天气影响,气溶胶粒径谱宽增宽;气溶胶数浓度较背景可上升约2~3倍,且气溶胶数浓度大值区呈悬垂状态分布,粒子数浓度大值层位于4000~4500 m和3000~4000 m高度;对沙尘气溶胶数浓度贡献最大的细粒子和粗粒子粒径分别为1.2~1.8μm和6.5~16.6μm,且气溶胶数浓度的增大在粗粒子段更为明显。气溶胶来源及输送层、以及气象要素垂直分布演变在气溶胶垂直分布及谱分布中发挥了重要作用。

Understanding the vertical distribution characteristics of aerosols in dust weather is crucial for further discussion of aerosol-cloud interaction and its impacts on weather and climate.In response to a dust storm in Northwest China on 6 September 2023,Gansu Weather Modification Office conducts aircraft detection and operational flights on north slope of the Qilian Mountains,obtaining the vertical detection data of aerosols.The vertical distribution of aerosols in dust weather is analyzed,and causes of vertical distribution of dust aerosols,related meteorological factors and air mass sources are studied.Results show that the dust weather is formed under the combined action of the upper front area and the surface cold high pressure.Affected by the dust weather,the peak mass concentration of PM10 and PM2.5 reaches 1150μg·m^(-3) and 282μg·m^(-3),respectively,at Wuwei Environmental Monitoring Station on north slope of the Qilian Mountains.Under the influence of dust weather,aerosol particles across all size segment show an increase in number concentration and particle size.Most of the dust particles are 1.2-1.8μm and 6.5-16.6μm in size,and there is a large concentration of aerosol particle number at the height of 4000-4500 m and 3000-4000 m.In addition,compared with the average concentration of particles in the fine particle segment and the coarse particle segment,the average concentration of particles increases by 2 times and 3.5 times,respectively.The average particle size increases by 3 times and 1.5 times,respectively.After the transit of sand and dust,the spectrum width widens,and the high-value region of the number concentration shows an overhanging state.In the coarse particle segment,the distribution of aerosol particle spectra changes from bimodal to trimodal.The increase in aerosol particle number concentration is more pronounced in the coarse particle segment and the lower layer.At the altitude of 500-2000 m above the ground,aerosol particles mainly come from the Gurbantunggut Desert in Xinjiang,while at the altitude of 2000-3000 m,aerosol particles mainly come from the Badain Jaran Desert in Inner Mongolia.In addition,the vertical upward movement in the middle layer and the strong northwest wind speed in the lower layer may play an important role in the vertical and spectral distribution of aerosols.Various sources and transport layers of aerosols,along with the vertical distribution evolution of meteorological elements,play an important role in the vertical distribution and spectral distribution of aerosols.